envvardoc: new tool to find undocumented env vars.

This tool will walk over interesting directories (-srcDirs flag) in the
source tree and look for references to environement variables. It then
cross-references these with environment variables found in a documentaion file
(-doc flag).  Any values found in source but not documented are printed to the
screen, and the exit code is set to non-zero.  Not all environment variables
are considered, only those matching one of the prefixes (-prefixes flag).

The change also begins the process of documenting environment variables.

Change-Id: Ie122b64b7befcb3104b960cf3d2d22bae443f67f
sync: delay copy retry on specific errors

http://camlistore.org/issue/206

Change-Id: I1dd07149352e3af6b39bcb86ed2312f19c3bae30
Merge "sync: delay copy retry on specific errors"
Merge "envvardoc: new tool to find undocumented env vars."
camput: have cache and stat cache based on github.com/cznic/kv

Added pkg/kvutil/kvutil.Open for convenience

Change-Id: Ie8db58e2c644a7358f252548bc57cccff7627497
Merge "camput: have cache and stat cache based on github.com/cznic/kv"
Small changes to UI. Very quick, very dirty.