Activate and fix updateRecurringTasks(), remove redundant methods
Shifted filenames to Controller

Storage now requires input filenames, but also has flexiblity of storing
in different files. Enables dog fooding while unit/system testing
Simplify LogicHandler.
getDateAsString() support for null start/end
Merge branch 'master' of https://github.com/cs2103aug2014-w14-1j/main
Merge branch 'master' into daryl_storage