[CodeAssist] Logical sort of proposals.

Improve the sorting of proposals, so that "logical" sort is used: if there are
numeric parts in the strings, these are compared as numbers instead of purely
lexicographically.

Thus, the list: [item1, item10, item1b, item2]
gets sorted as: [item1, item1b, item2, item10]

Change-Id: I16a0106d9dc9bb27731f96c3f180ad20cd9a44f5
Reviewed-by: Leandro Melo <leandro.melo@nokia.com>