Fix #394, #407, #406

[fragm3]

Fixes #394, #407, #406 Closed https://github.com/fossasia/susi_chromebot/pull/399, due to merge conflicts which couldn't be solved, not detected in my IDE.

Checklist

• [x] I have read the Contribution & Best practices Guide and my PR follows them.
• [x] My branch is up-to-date with the Upstream master branch.
• [x] The unit tests pass locally with my changes
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation (if appropriate)
• [x] All the functions created/modified in this PR contain relevant docstrings.

Short description of what this resolves:

Adds single material icon for sending message or using voice input, like in web chat. GIF:

Changes proposed in this pull request:

• Change naming for submit in options.js: Naming submit1, submit2, submit3 meaningfully
• Solves: Uncaught TypeError: Cannot read property 'addEventListener' of null at options.js:106
• Modify Compose Message Similar to Web App

[fragm3]

@zamhaq @Orbiter @gabru-md @ms10398 @rupav please review.

[fragm3]

@zamhaq @Orbiter @gabru-md @ms10398 @rupav please review.

[mariobehling]

Ok, thanks. I am merging this as a good step forward. Please make it easier for reviewers in future by separating different PRs. Thanks! Good job.