chore(emacs/lean-mode): add package info
feat(emacs/lean-option): provide candidates and validation for lean-set-option

Close #106
fix(frontends/lean/info_manager): user provided options override saved options, fixes #119

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/data/subtype): elaborator does not need help anymore (i.e., 'show'-expression) for this file

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/data/list): avoid placeholders '_', make first argument of false_elim implicit

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(emacs/lean-cmd): add lean-clear-cache

Close #99
feat(bin/linja): add clear-cache target

Close #99
feat(library/data/category.lean): add very basic category theory