Add developer scripts

Automates the procedure documented in CONTRIBUTING.md
Overhaul USAGE.md

- Include all current commands
- Use new functionality to skip explicit "brew tap" commands
- Document all forms for specifying Casks (URI, etc)
- Demote "Additional Taps" section to near the end
- Other small tweaks too numerous to list
Spin out HACKING.md from CONTRIBUTING.md

Create a bunch of guidelines/FAQs based on stuff gleaned from
PR discussions and IRC.  Obviously this is just a starting
point.
Add project_stats script

Queries git database to get statistics on project or release.
Usage in project_stats -help
add missing user feedback during pkg uninstall

Consistent between uninstall keys.  Also give initial feedback
first, before any other action.
Update: Java 1.7.0_51

Update formula based on Issue #2441 and suggested formula by @hevisko.
Edits to suggested formula follow suggestions from @rolandwalker and
the homebrew-cask contributing guidelines.
Electrum 1.9.7
Merge pull request #2443 from goxberry/java-7u51

WIP: Java 1.7.0_51
java: add caveats for GUI applications as Eclipse
Merge pull request #2450 from eugenesan/java

Update to JDK7 u51 and add caveats for GUI applications
Pandoc 1.12.3
Created Cask for SoundCleod
Phoenix Slides 1.3
Poedit 1.6.3b
QuoteFix for Mac 2.5.2
Rest Client 3.2.2
Merge pull request #2452 from bluemaex/master

Created Cask for SoundCleod
updated shotcut
Merge pull request #2454 from vitorgalvao/update-shotcut

updated shotcut
tikz-editor.rb Cask missing .app extension

fails install without this change