Bug fixes and improvements for interest post publishing and scheduling

[x] Disabled publish button when title and description are empty
[x] Removed scheduleAt when it's not checked and set
[x] Added the support of setting the time along with the date on scheduling posts
[x] Set a minimum time to schedule posts (which should be greater than the current time by at least 1 hour)
[x] Improved usability on post scheduling (previously user wasn't able to change the schedule time once set)
[x] Minor UI changes

gayanSandamal / choner-mobile