Don't install crypto libs to root filesystem (or require root to build)

The current build system has two (related) problems:
1. it installs all the required crypto libraries *during the build step* to a hard-coded globally viewable path
2. it uses sudo during the build step (required due to problem (1) ).

This patch modifies the makefiles to use crypto libraries checked out as part of the project. Note that for the OTExtension submodule, this required changes in the module itself (hence it was also forked). 
The patch also allows installation to other directories by modifying the "prefix" make variable.