Add field! for property!

[c910335]

relate: #57, #120, #144, #171

This PR supports the two syntaxes in #171 by #57.

For example:

class Foo < Granite::ORM::Base
  # ...
  field number : Int32
end

foo = Foo.new(number: 0)
foo.number += 1

This gives:

Error in src/test.cr:7: undefined method '+' for Nil (compile-time type is (Int32 | Nil))

foo.number += 1
^

Rerun with --error-trace to show a complete error trace.

It is still annoying to use foo.number = foo.number! + 1.

With this PR:

class Foo < Granite::ORM::Base
  # ...
  field! number : Int32
end

foo = Foo.new(number: 0)
foo.number += 1 # It works!

This PR also includes the change from type to options in #120 because it is easier to implement field! with this feature.
This PR also removes the property in table.cr because it is duplicated.

[eliasjpr]

🥇

Should we add specs for this?

[c910335]

@faustinoaq
Specs were done. 😄

[faustinoaq]

🎉