Fix Mac packager to build proper application bundle and include Client icon

[PropGit]

Edit: This started as a small issue but was found to be a big problem - the application bundle was not being generated properly, preventing it from appearing in the Mac's Launchpad or Spotlight after install, making it near impossible for typical users to launch the BlocklyPropClient app.

Old Description:
The BlocklyPropClient icon is not included in the current package.

Manually including the icon in various ways within the bundle does not seem to fix the problem.

Research and fix the application icon issue in Mac application bundle / package.

[PropGit]

Can not determine what is causing the problem here. Will release without this fix for now.

Update: This was found to be a problem with the macos.spec file used by the PyInstaller build step. See next post.

[PropGit]

Found that the cause of all these problems was ultimately due to a malformed macos.spec file.

Determined that the file could be recreated, the proper bundle format requested, the application icon included and the bundle identifier specified using pyi-makespec --windowed --icon BlocklyPropClient.icns --osx-bundle-identifier com.ParallaxInc.BlocklyPropClient --noupx BlocklyPropClient.py

Afterwards, a few modifications to the .spec were required to include the propeller-tools files, the about.txt, and set the application version number.

All this was done in PR #67.

The ugly details will be moved from the README.me to the repo's wiki soon.

[PropGit]

Once we get Issue #66 addressed, I will test more on my machine and then organize a test of a couple other machines.

[PropGit]

Removed one manual change to the .macos.spec file (to leave the Mac application bundle version number unset- 0.0.0) and moved that responsibility over to the mac_app_sign_and_package script - a more fitting place for it. This was done in PR #74.

[PropGit]

Issue #66 completed and PR #74 merged. Build for Mac produces a application bundle which works properly until it's installed and launched with the normal means: from Finder or LaunchPad. This seems to be an issue with retrieving the home directory to convert the relative Propeller-Load executable path to an absolute path, described in this BlocklyProp Issue, which, it turns out, is really a Client issue.

[PropGit]

PR #77 fixed above failure. The call to retrieve the working (application's) directory was responding with blank. Note this problem seems to still exist on Linux as of Issue #82.

Tested on 2 host machines (@PropGit, @MatzElectronics) and two VMs (Yosemite and Sierra). App Bundle and packager deemed correct and ready for release.