Feature/feature contrib

A number of changes to bug, feature and refactor scripts to better manage their respective branches. In addition, the keywords to invoke functions (previously just "finish") has been expanded to allow multiple keywords to invoke the same function (i.e. finish, fin, end or complete aliased to the finish function). 

Since the bug, feature and refactor scripts are nearly the same script, the common code has been extracted to another file (git_bug_feature_refactor) that is sourced so that changes are made once and do not need to be replicated to multiple files or have a divergent commands. Ideally this file should start to contain common routines used by other scripts for things like detecting if a branch exists or if the branch resides in the remote repository, etc. It probably should be named more appropriately for this function, like maybe git_extras_common. 

In addition, these scripts have been given the ability to list the the branches for the respective type of branch (i.e. git bug), create a branch (i.e. git bug fix_strlen) if the branch does not exist, switch to the branch (i.e. git bug fix_strlen) if the branch does exist, merge the branch back into the integration branch (i.e. git bug finish fix_strlen) or delete the branch entirely (i.e. git bug delete fix_strlen).