add init.m

* add function signatures for init and clone
* in log, delete the reply, if there is one, in addition to the prompt
add the init command to initialize git repo

* add 'update' option to add command
* update JGit help comments with add('update') and init
* replace 'notepad' EDITOR with getEDITOR which checks system type and assigns correct default system editor, mac=textedit, linux=gedit
* add some comments to constant properties
* add VALID property, checks if javaclasspath and jar package are valid - this makes it easier to install JGit, and only checks the classpath once, when JGit is instantiated - also matches install directions.
* add VERSION and VERFILE a text file with version number - so using downloadJGitJar can be used to update JGit if out of date
* remove validation getGitAPI to validateJavaclasspath which is more appropriate
* fix all error identifiers to start with "jgit" not git!
* add at least the first line of help for each function
* fix validateJavaClassPath to return error message if not valid by using if-else-end instead of return.
* print version to file in downloadJGitJar
* new getEDITOR function
* add help to add command
* use inputparser and add update option
* create addCMD, add all files first then call addCMD.call, not each loop!
* create custom validator for pathlist
* add help to commit, comments and code cell titles
* don't return git or anything from any functions!
* fix java.lang.String needs char, need newline and need class for constant property
* add trailing end for log
* add version file, easiest if this already exists, so just include it in repo and deploy
Merge branch 'master' of github.com:mikofski/JGit4MATLAB