Update apps design to match 4.0 overal styling and components

We need to update the app design to make it more consisten with Moodle LMS and to use modern lines/design patterns.

• For iOS remove the BACK text at the top bar and align text to side left.
• Show only manual completion on course contents for activities without page.
• Create new item divider, title like for section titles.
• Show more on activity description and info

Related changes:

• https://github.com/moodlehq/moodleapp/pull/3063
• https://github.com/moodlehq/moodleapp/pull/3066
• https://github.com/moodlehq/moodleapp/pull/3073
• https://github.com/moodlehq/moodleapp/pull/3100
• https://github.com/moodlehq/moodleapp/pull/3108
• https://github.com/moodlehq/moodleapp/pull/3111
• https://github.com/moodlehq/moodleapp/pull/3113
• https://github.com/moodlehq/moodleapp/pull/3121
• https://github.com/moodlehq/moodleapp/pull/3130
• https://github.com/moodlehq/moodleapp/pull/3146
• https://github.com/moodlehq/moodleapp/pull/3149
• https://github.com/moodlehq/moodleapp/pull/3154
• https://github.com/moodlehq/moodleapp/pull/3155
• https://github.com/moodlehq/moodleapp/pull/3156
• https://github.com/moodlehq/moodleapp/pull/3162
• https://github.com/moodlehq/moodleapp/pull/3165
• https://github.com/moodlehq/moodleapp/pull/3168
• https://github.com/moodlehq/moodleapp/pull/3172
• https://github.com/moodlehq/moodleapp/pull/3175