added reason for 423 error message

Added Reason Code to the 423 Error Message. Clients applications can better detect the status of the lock error and correctly handle their flow. The Reason is a string code placed at the end to the error message an has this form:

"[" + RCODE(fixed-tag) + ":" + REASON-CODE(2-char-code) + TTL(sec-number) + "]"

The REASON-CODE possible values are:

• WL: The dataset is write locked
• RL: The dataset is read locked
• CL: The dataset can't be locked (lock cache mutex can't be acquired)
• CU: The dataset can't be unlocked (lock cache mutex can't be released)

For example:

[seismic-store] The dataset is write locked [RCODE:WL3600]

swagger documentation updated.