Corrección de strings
Agregar ScrollView
Interfaz del menú principal lista.
Funcionalidad del menú principal
Main Menu
Imágenes del menú principal
Merge branch 'master' of https://github.com/chidmdxx/SOFIA.git

Conflicts:
	SOFIA/AndroidManifest.xml
	SOFIA/src/mx/udlap/sofia/Interfaz.java
	SOFIA/src/mx/udlap/sofia/Seeanswer_exercises.java
	SOFIA/src/mx/udlap/sofia/Solve_exercises.java
	SOFIA/src/mx/udlap/sofia/Solve_solver.java
	SOFIA/src/mx/udlap/sofia/Theory_description.java
	SOFIA/src/mx/udlap/sofia/Theory_exercises.java