Restructuring selenium tests

[smarshy]

All selenium tests have been restructured to share code in this PR. Functions which could be possibly reused have been identified and created for the tests. In most tests, constants have also been isolated at the top so that any change in UI only requires a change at the beginning of the file.
There is reduction in both test times and lines as follows -
Time (approx. ) - 74 min to 44 min (around 41-42% reduction)
Lines reduced due to removal of duplication and unnecessary imports in tests files - approx 30% (7527 to 5300)

Travis build timings also have similar reduction ( from approx. 16 to 9 min ~ 43%)

Number of tests have also increased from 164 to 168 but these are not new tests. I have broken subparts of a few tests into separate ones as they were repeatedly testing the same thing

Related to #369

[coveralls]

Coverage increased (+0.2%) to 83.944% when pulling d646fa9 on smarshy:refactor-sel into 2852db6 on systers:develop.

[tapaswenipathak]

9 min 54 sec. Great! 😄 👍