refactor(kernel/metavar): switch to functional substitution datastructure

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(lua): reactivate some of the Lua unit tests

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/kernel_bindings): reactive some of the kernel Lua bindings

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(*): add pushboolean inline function, and replace lua_pushboolean with it

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(*): add pushinteger and pushnumeral inline functions

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/kernel_bindings): new level Lua API

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
chore(.travis.yml): remove automatic copy to bitbucket

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>