Log messages updated

[shreyas-damle]

Updated log messages:

• Added [Dashboard], [App Details] and [Delete App] identifiers to identify the page from where the message was originated.
• Made messages more specific and unique so that we can identify exact location easily.

Sample logs:

DEBUG:    [Dashboard]: Metadata file path ~/.pebblo/shreyas-test-dir//metadata/metadata.json
DEBUG:    Reading content from file: ~/.pebblo/shreyas-test-dir//metadata/metadata.json
DEBUG:    Exception: File not found at path /Users/shreyasdamle/.pebblo/shreyas-test-dir//metadata/metadata.json
DEBUG:    [Dashboard]: Metadata file /metadata/metadata.json not found for app: shreyas-test-dir.
WARNING:  [Dashboard]: Metadata file is not present for application: shreyas-test-dir,skipping application