CB-5900 Spelling fixes for English docs

Fixes some spelling and casing errors in the English version of the docs
CB-5387 Make given example a working example
CB-5908: fix up inconsistencies and clarify

The Android instructions were inconsistent in the filename of the splash
screen. And with the addition of the splash screen images to the Android
project template, the instructions have changed and are more simple.
CB-5294: Add input type=file Android quirk
Updated iOS Upgrading doc.