Relative paths plus default settings

The default settings script file which user can override by user_settings script file.
    - There's new variable, PROJECT_ROOT which defines the location from root.

Export/build can be redirected to any directory within the root project dir. Using syntax:
<pre>
project_dir:
   path:
   name:
</pre>
It allows to define a generic path and then specific name for tools or generic name.

One potential output can be:
<pre>
examples/blinky
examples/blinky/uvision/k20.file
examples/blinky/uvision/lpc1768.file
examples/blinky/makefile_gcc_arm/Makefile
examples/blinky/coide/k20.file
</pre>

I'll be running more tests before merging. Open for review.