Bug 1094302 - Remove unused EXTRA_JS_MODULES rule from rules.mk; r=glandium

The installation rule for EXTRA_JS_MODULES and EXTRA_PP_JS_MODULES
became unused after b961ba8f0892 (bug 1044162). We remove the dead code.

--HG--
extra : rebase_source : 40adf7514d15ae4ba5bbfe3ac101061657aac841
Bug 1094302 - Move JS module installation into the misc tier; r=glandium

JS module installation performs simple file copying or preprocessing.
There is no reason it can't occur in parallel. Move it to the misc tier.

As part of this, I recognized that TESTING_JS_MODULES was assigned to a
tier. Since these files are managed by an install manifest, they don't
belong to any tier. So the tier is now listed as None.

--HG--
extra : rebase_source : 963f0813e43802c017837ce9d55f8e666decd76a