Move docs section about build plugins even further

Sashko should probably review this
Prefer backticks in markdown for code
Change the example url to example.com
In the absence of the mobile control file it should be treated as an empty file
Change other example fields
Parse files extensions other than png
Commit the .npm folder for xmlbuilder package
Pass the appId to the application process in an env variable

Since it is passed only in the development mode it can be used for nifty things
like distinguishing mobile apps by a tuple of (id, server-url)
Split out android prereqs from android bundle installation
Work around fstream weirdnesses.

Before this fix, we were producing tarballs that npm 'tar' couldn't
untar if the first file inside the top-level directory was not
writeable. (Which was indeed the case since the unipackage -> isopack
change, which resulted in isopack.json being the first file in built
package tarballs.) See comment for more explanation.
Creating android --getready command
Whitespace
Fix building for mobile targets w/o a mobile control file
Fix actually using the new config.xml in the new mobile build flow
Whitespace
AppId-dependant HCP
Merge branch '0.9.3.1' into 0.9.4-pre.2

Conflicts:
	History.md
	packages/meteor-tool/package.js
	packages/package-version-parser/package.js
	scripts/admin/banners.json
	scripts/admin/meteor-release-experimental.json
Check for meteor avd
Work around fstream weirdnesses.

Before this fix, we were producing tarballs that npm 'tar' couldn't
untar if the first file inside the top-level directory was not
writeable. (Which was indeed the case since the unipackage -> isopack
change, which resulted in isopack.json being the first file in built
package tarballs.) See comment for more explanation.
Bump minimongo version number