Set versions in .info files to 1.7-dev

src/cambridge/cambridge.info

 name = "University of Cambridge"
 description = "Install the standard University of Cambridge features."
-version = 7.x-1.6
+version = 7.x-1.7-dev
 core = 7.x
 
 ; core

src/cambridge_lite/cambridge_lite.info

 name = "University of Cambridge (lite)"
 description = "Install the core University of Cambridge features."
-version = 7.x-1.6
+version = 7.x-1.7-dev
 core = 7.x
 
 ; core