Added the "gck" alias for "git config".
Added the gcka function which answers a value for a given Git config key for all projects in current directory.

* Updated the gea function to call the gcka function to keep code DRY.
* Fixed comment type where "products" should have been "projects".
Renamed the gck alias to gkey for clarity.
Renamed the gcka function to gkeya for readability and compatibility with aliases.
Renamed the gea function to gaila for compatibility with the gail alias.
Added the gseta function for setting a key=value pair for all projects in current directory.

* Updated the gsea function to reference the gseta funtion.
Renamed all gkey aliases and functions to gget.

* Allows one to think in terms of getters and setters for the Git config instead of keys and values.
Renamed the following functions: gsea -> gailsa, gusa -> gunseta for name clarity.

* The gailsa function name is now compatible with the gail aliases and related functions.
* The gunseta function is now in the same family of naming conventions as the gset functions.
* Cleaned up function documentation and parameter definitions.