Drop unnecessary file I/O handling + Auto-Detect Configuration Format

[caronc]

Description:

The following changes come bundled in this Pull Request (PR):

• Code clean up can be done with AppriseConfig.add_config() function and the new ConfigMemory() type (introduced in PR apprise/199) which eliminates the need to write the configuration to a file just so that it can be re-read.
• Configuration format can be auto-detected now (when deciding if it is YAML or TEXT)

Note: Test cases won't pass until PR apprise/282 makes it upstream into the official version. The requirements.txt has already been updated to point to it. For this reason this PR will remain open until Apprise catches up. Code has been tested to work great against the Apprise/Master branch though.

Checklist

• [x] The code change is tested and works locally.
• [x] There is no commented out code in this PR.
• [x] No lint errors (use flake8)
• [x] tests added

[codecov-commenter]

Codecov Report

Merging #18 into master will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #18   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          335       321   -14     
=========================================
- Hits           335       321   -14     

Impacted Files	Coverage Δ
apprise_api/api/forms.py	100.00% <100.00%> (ø)
apprise_api/api/views.py	100.00% <100.00%> (ø)

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