Install targets use CMAKE_PREFIX_PATH instead of CMAKE_INSTALL_PREFIX

[dgavedissian]

When installing software built with CMake, it should be installed to the path specified by CMAKE_INSTALL_PREFIX. A pull request has added install targets to install to CMAKE_PREFIX_PATH, which is incorrect. CMAKE_PREFIX_PATH is used for FIND_XX scripts to search for dependencies to the project you're currently building.

These need to be changed to remove the explicit ${CMAKE_PREFIX_PATH} from the install targets. I'll create a pull request to fix this.