ecore_con: clean up, refactor and unpdate documentation.

ecore_con: clean up, refactor and unpdate documentation.

Summary:
1. Have refactored code in ecore_con_local.c
2. Changed env variable from "TMP" to "TMPDIR".
3. Added check for negetive port number when type is ECORE_CON_LOCAL_USER.
4. Added check to check TMPDIR before assuming /tmp as temp directory.
5. Updated documentation in Ecore_Con.h explaining about local socket and port number.

Signed-off-by: Srivardhan Hebbar <sri.hebbar@samsung.com>
Reviewers: cedric

Reviewed By: cedric

Subscribers: cedric

Differential Revision: https://phab.enlightenment.org/D2194

Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>