Add client-side msg_name_and_crc -> msg_index table

Add client-side msg_name_and_crc -> msg_index table

vppapigen now generates per-message crcs. Verified that whitespace
and real changes in message A don't change the crc for message B, etc.

Fixed the sample and flowperpkt plugins to participate. Others need
the same treatment. They don't build due to python/java language binding
build issues.

To use the scheme:

Client connects as usual.

Then call: u32 vl_api_get_msg_index(char * name_and_crc)
name_and_crc is a string like: "flowperpkt_tx_interface_add_del_753301f3",
aka the message name with _%08x <expected crc> appended.

Try these vpp-api-test commands to play with it:

vat# dump_msg_api_table
     <snip>
 [366]: punt_reply_cca27fbe
 [367]: ipsec_spd_dump_5e9ae88e
 [368]: ipsec_spd_details_6f7821b0
 [369]: sample_macswap_enable_disable_0f2813e2
 [370]: sample_macswap_enable_disable_reply_476738e5
 [371]: flowperpkt_tx_interface_add_del_753301f3
 [372]: flowperpkt_tx_interface_add_del_reply_d47e6e0b

vat# get_msg_id sample_macswap_enable_disable_reply_476738e5
 'sample_macswap_enable_disable_reply_476738e5' has message index 370

vat# get_msg_id sample_macswap_enable_disable_reply_476738e3
 'sample_macswap_enable_disable_reply_476738e3' not found

CRCs may vary, etc.

vppapigen is used to build a set of JSON representations
of each API file from vpp-api/Makefile.am and that is in
turn used by each language binding (Java, Python, Lua).

Change-Id: I3d64582e779dac5f20cddec79c562c288d8fd9c6
Signed-off-by: Dave Barach <dave@barachs.net>
Signed-off-by: Ole Troan <ot@cisco.com>