Merge pull request #361 from benma/otstring_cleanup

Don't use OTString in OTSocket.
OTString: rename class to String
OTString: rename files to String.{h,c}pp
Merge pull request #360 from toxeus/renameOTString

OTString: rename class to String
Reorder sequence in CMakeFiles.txt

Initialize submodules before checking third party libraries.
Merge pull request #362 from mhamrle/cmake_reorder

Reorder sequence in CMakeFiles.txt