Add basic pinning functionality

If a file conda-meta/pinned is in an environment the lines of that file will
be added to the specs with every install. If the package is explicitly
included in the command line, it overrides the pin.

This does not yet affect conda remove.
Don't automatically override pinned packages

You can override all pinning with the --no-pin flag.
Added lsfiles command to list all files belonging to specified package
Fix for spaces in install directory and in env names
Improved lsfiles command according to discussion from pull request (#659)
Corrected ignorePredefinedFiles condition in walk_prefix call
Corrected code to be compatible with PEP-0008

1. Adjusted names of functions and variables.
2. Rewrite compare operations of boolean values.
Merge pull request #659 from mutirri/feature-lsfiles

Added lsfiles command to list all files belonging to specified package
Update CHANGELOG
Update list of conda-build commands
Merge branch 'master' into pin

Conflicts:
	conda/cli/install.py
	conda/plan.py
Check for pinning in conda remove
Merge pull request #640 from conda/pin

Add basic pinning functionality
Update CHANGELOG
allow no_link file, see issue #678
Improve an error message
Correctly handle an empty pinned file
Merge branch 'master' of github.com:conda/conda
Remove unncessary comment
Make sure message is always printed on its own line