Provide script functionality for creating update mirrors

Update mirrors are the differences between versions
 We have several ways for creating mirrors:
 1) simple comparation of two mirror folders (the easyest way)
   Should be run on server (or client) where we have two
   ready mirrors (for example for ver. 5.1 and 6.0)
   6.0 - 5.1 = update_mirror
 2) more complex implementation (good for make process)
   in this case we build PRODUCT_VERSION mirror and then
   download and process the difference in packages
   between PRODUCT_VERSION..master (Works good for RPM,
   not so good fo DEB).

Implements-blueprint: generating-update-mirrors

Provide draft

Change-Id: Ib7650a74067bf4f3485785dae2dd7b52c8d9be8a

Complete Re-design. Create centos_update mirror

Change-Id: I3572e88cf92342201732341b138d846328ebb957

Fix some typos

Change-Id: I75435c86f72955f8d2d452fc18df851176f0a29c

Improve version support

Change-Id: I86751692d1c97b3702c041a69451833fdaf20e46

Fix var name

Change-Id: I83d1260a7ac7b5a574ce4b9a38548f2ac2f2e06a

Fix variables names in sed

Change-Id: I27555ddd7c28519717750c0cbc428962f5d4965c

Refactoring update process

Change-Id: I7a6fc58ccffc0c7752779a759c76bdade84ceb9a

Improve removal prcedure for centos_update folder

Change-Id: I2be78dbde70ea33028aee8e159639123ddb632ac

Add check for update packages

Change-Id: I0c0d9fe89a25c70cd124078d90afd9f65fc6d153

Rename file to create_centos_update_mirror.sh

Change-Id: I6fdc45745ef109ee61cf900d3242ab7f95a53e70

Create ubuntu_updates mirror script

Change-Id: I2c1dfd9d572ab21795d664ae2ea899ae2bd04cae

Update centos script

Change-Id: Ibac3efe68f8a0b0e23f183edd1c75f406f2a9dc9

Fix -z check for variable

Change-Id: I7e7eebf81f6822c7e7df5d0c28b2e597fe0fadca

Server version for craeting mirrors

Change-Id: Ic208b28e87a1505fe12317494ad327841c9a0964