Add borg check and rename options

Because we added borg check functionality, some of the Options have been
renamed:
-C -> -V
-E -> -e (as it is a sub)

-C: check
-y: --verify-data
-p: prefix or glob for check

Internal variables with CHECK have been renamed or changed to VERIFY

Borg -C without any extra parameters is equal to borg check.
-y adds the --verify-data and -p is a mix of the -P and -a options. If
there is a "*" in the option then -a will be used, else -P

Note that repair command has to be run manually. Run -C with -v
(verbose) to see the repair command structure.

borg check can take a long time on very large repositories.

Readme.md

@@ -59,15 +59,24 @@ override the default borg executable found in path
 ### `-P`
 print list of archives created
 
-### `-C`
-check if repository exists, if not abort
+### `-V`
+verify if repository exists, if not abort
 
-### `-E`
+### `-e`
 exit after check
 
 ### `-I`
 init repository (must be run first)
 
+### `-C`
+run `borg check` over given repository
+
+#### `-y`
+Add `--verify-data` to `borg check`. Only works with `-C`
+
+#### `-p <prefix|glob>`
+Only `borg check` data that has given prefix or glob (with *). Only works with `-C`
+
 ### `-i`
 print out only info