convert installed modules to Config.cmake format

[guruofquality]

• rewrite FindPothos.cmake to PothosConfig.cmake
• affects sub-projects usage
• pothos-python installs modules as well

[guruofquality]

https://github.com/pothosware/pothos/commit/c1ee7d5c351e4495d1edc89914b8ffade2e110b3