refactor(library/logic/connectives/eq): simplify eq_rec_on_id proof

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/logic/connectives/basic): add not_not_em theorem

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(frontends/lean/info_manager): store environment+options in the info_manager, fixes #96

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(emacs/lean-info): type of a symbol at the end of buffer
fix(emacs/lean-info): handle when both identifier and symbol info exist

Example: library/data/int/basic.lean file (398, 22)

The '+' symbol is attached with both of identifier info and symbol info

-- SYMBOL|398|22
+
-- ACK
-- IDENTIFIER|398|22
int.add
-- ACK