Allow executing the makefile from other directories

[omorandi]

By creating an alias like the following:

alias maketi='make -f /patht/to/MakeTi/Makefile'

there's no need to copy the repo in each Ti project

[mattapperson]

This needs to be optional before I can merge it in... aka when the flag is set, use it, else use the project dir variable

[omorandi]

With this change the makefile would work seamlessly in either case.
The MAKETI_DIR variable will always point to the directory containing the Makefile, so when the MakeTi files are copied in a Ti project, it will point to the enclosing project directory (as expected). My point however is making the bin/titanium.sh script correctly executable also when the makefile is invoked from a Ti project directory not containing the MakeTi makefile + support scripts....

[mattapperson]

Ahh I see what you did there :)

[omorandi]

;-) thanks!