feat(frontents/lean/parser_cmds):
Print the type of variables introduced by definition, hypothesis (variable) or proof.
fix(kernel/level): bug reported by Floris

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean/parser_cmds): add 'print definition' command

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(emacs): add shortcut for executing Lean without loading the kernel

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(kernel/kernel_exception.h): change application error messages

Error messages are now of the form:
Error: in application
    foo bar
Argument
    bar
has type
    baz
the expected type is
    baz'
feat(kernel/type_checker_justification.cpp): improve error message for type errors on application.
feat(/kernel/type_checker_justification): add better error messages for type mismatch in application.

Fix formatting, correct primes (broken for testing error messages).
test(*): adjust tests due to changes in the error messages

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
chore(kernel/type_checker_justification): fix style

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
doc(examples/lean): adjust examples due to changes in error messages

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(frontends/lean/parser_cmds): update help and error messages