refactor(library/logic/basic): rename absurd_elim to absurd, delete contrapos and trivial_not_true theorems

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/logic): rename connectives -> core, basic -> connectives
feat(frontends/lean/server): preserve info that occurs in columns before first changed column

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean/server): add ECHO command for debugging purposes

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(tests/lean/interactive): add --server test

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(src/emacs): add 'begin' reserved keyword

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/data/nat): mark more arguments implicit

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library): more implicit_args for: and_assoc, and_comm, or_assoc, or_comm, if_pos, if_neg

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(src/emacs/lean-syntax.el): remove obsolete command set_opaque

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(src/emacs/lean-syntax.el): add commonly used operators

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
chore(library): minor cleanup

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library): move more notation to general_notation
feat(library/data/nat/div.lean): remove dependence on funext