Add custom loader for Powershell, improve its implementation in Cmder

Fixes #104, fixes #53, fixes #65 (my bad), related to #136, and should
fix #139
Merge pull request #272 from bliker/master

Update Dev Branch
Merge pull request #271 from LeoColomb/master

Add custom loader for Powershell & improve its implementation
Add a lua script to clean the aliases file

Note that cmder doesn't ship with lua. Next step is converting this
script to perl, which ships with msysgit.
Convert the clean alias script to perl
remove lua version
Add an error message if an alias is detected as invalid
Don't ignore icons when packing (Fixes #292)

Icons were being ignored and causing the `/REGISTER ALL *` command to
give the context menu option a broken image..
Adding history alias

simple alias that operates as history command
Merge pull request #299 from robgithub/development

Adding history alias
Merge pull request #300 from melku/clean_aliases_script

Clean aliases script
Add option to reload aliases from file

Add a quick way to reload the aliases file in the current shell using:

    alias /reload
Merge pull request #304 from glucas/pull-alias-reload

Add option to reload aliases from file
Add an unalias command

Add bin/unalias.bat to perform the opposite action of alias.bat.
Removes a given alias from the current shell environment and the
aliases file.

Fixes issue #281.
Merge pull request #313 from glucas/unalias-command

Add an unalias command
Update msysgit & conemu

Updated links to latest versions of msysgit and conemu; 1.9.4-preview20140929 and 141117 respectively.
changes copied from https://github.com/TheCjw/cmder/commit/0f295234cc95427ccef82bb23c5493d3abeb7a57 and https://github.com/TheCjw/cmder/commit/18fea0ac0375b912eb0b3fd7a9dff14893d50b92
Merge pull request #326 from kohenkatz/development

changes copied from PR#256
Adding script to enable SSH-agent #193

Adding agent-script to bin-folder and a commented out call in init.bat
Adding info on SSH agent to README.md