add a make check-local command to verify the i18n string formatting

When I do i18n translation, I find some string formattings are wrong.
So I add a check-local command to help the developer to check their
string formatting.

Every developers please run this command before submit your patch.

After you run this command, it may report some invalid string
formattings as follow.
$ make check-local
Checking for invalid i18n string...
bad i18n string formatting:
  KCHAPI0005E: Create is not allowed for %(resource).
make: *** [check-local] Error 1

You should check %(resource) is what you want.

Ref:
https://docs.python.org/2/library/stdtypes.html#string-formatting-operations

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Signed-off-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com>
Signed-off-by: Christy Perez <christy@linux.vnet.ibm.com>
remove obsolete i18n strings which are no longer in use

These strings are no longer in use, but they still remain in i18n.py

Signed-off-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com>
Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
add a method to check the i18n strings are obsolete

There are some i18n strings are no longer in use in source code.
But they are still remain in i18n.py.

We should add a mechanism to check the obsolete i18n strings.

Signed-off-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com>
Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>