Use Java8 syntax (lambdas, <>), drop unused dependencies

[zbynek]

Same idea as https://github.com/javacc/javaccPlugin/pull/48 , but using Java8 syntax

[codecov-commenter]

Codecov Report

Base: 87.73% // Head: 87.90% // Increases project coverage by +0.17% :tada:

Coverage data is based on head (e99746c) compared to base (59cd9f7). Patch coverage: 91.66% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #61 +/- ## ============================================ + Coverage 87.73% 87.90% +0.17% - Complexity 149 150 +1 ============================================ Files 23 23 Lines 432 430 -2 Branches 28 28 ============================================ - Hits 379 378 -1 + Misses 49 48 -1 Partials 4 4 ``` | [Impacted Files](https://codecov.io/gh/javacc/javaccPlugin/pull/61?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [.../org/javacc/plugin/gradle/javacc/JavaccPlugin.java](https://codecov.io/gh/javacc/javaccPlugin/pull/61?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3VicHJvamVjdHMvcGx1Z2luL3NyYy9tYWluL2phdmEvb3JnL2phdmFjYy9wbHVnaW4vZ3JhZGxlL2phdmFjYy9KYXZhY2NQbHVnaW4uamF2YQ==) | `96.87% <75.00%> (+2.93%)` | :arrow_up: | | [...mpilationresults/CompiledJavaccFilesDirectory.java](https://codecov.io/gh/javacc/javaccPlugin/pull/61?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3VicHJvamVjdHMvcGx1Z2luL3NyYy9tYWluL2phdmEvb3JnL2phdmFjYy9wbHVnaW4vZ3JhZGxlL2phdmFjYy9jb21waWxhdGlvbnJlc3VsdHMvQ29tcGlsZWRKYXZhY2NGaWxlc0RpcmVjdG9yeS5qYXZh) | `100.00% <100.00%> (ø)` | | | [...mpiler/JavaccCompilerInputOutputConfiguration.java](https://codecov.io/gh/javacc/javaccPlugin/pull/61?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3VicHJvamVjdHMvcGx1Z2luL3NyYy9tYWluL2phdmEvb3JnL2phdmFjYy9wbHVnaW4vZ3JhZGxlL2phdmFjYy9jb21waWxlci9KYXZhY2NDb21waWxlcklucHV0T3V0cHV0Q29uZmlndXJhdGlvbi5qYXZh) | `96.77% <100.00%> (ø)` | | | [...e/javacc/programexecution/JjdocProgramInvoker.java](https://codecov.io/gh/javacc/javaccPlugin/pull/61?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3VicHJvamVjdHMvcGx1Z2luL3NyYy9tYWluL2phdmEvb3JnL2phdmFjYy9wbHVnaW4vZ3JhZGxlL2phdmFjYy9wcm9ncmFtZXhlY3V0aW9uL0pqZG9jUHJvZ3JhbUludm9rZXIuamF2YQ==) | `100.00% <100.00%> (ø)` | | | [...adle/javacc/programexecution/ProgramArguments.java](https://codecov.io/gh/javacc/javaccPlugin/pull/61?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3VicHJvamVjdHMvcGx1Z2luL3NyYy9tYWluL2phdmEvb3JnL2phdmFjYy9wbHVnaW4vZ3JhZGxlL2phdmFjYy9wcm9ncmFtZXhlY3V0aW9uL1Byb2dyYW1Bcmd1bWVudHMuamF2YQ==) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

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[zbynek]

@johnmartel I've been granted push access to this repo but I think it would be better if I only push changes seen/reviewed by another person. Will you have time to check this PR?

[johnmartel]

@zbynek I just had a look, sorry for the delay. This looks good to me. When I handed over the repository, I was well aware that the plugin needed a lot of upgrading in terms of supported Gradle versions, Javacc dependency and Java code in general. Thanks for making a step towards levelling up the codebase.

I am unfortunately not available for much involvement in this plugin's development, but I'm glad to see it lives :)