Fix captive portal login ssl error overflow

This patch fixes the built-in html page shown in the captive portal
login activity when there is an ssl error. The page is now scaled
correctly with respect to the device screen, and text wraps as
expected.

This patch also cleanups the hardcoded page by:
 - formatting it for better reading,
 - inlining the "px" css rules,
 - using string concatenation instead of format for including the
   localized text.

Bug: 62269512
Bug: 36532213
Test: manually triggered the activity to load the error page
Change-Id: I9d037222798bd9d4c1736923afb71e3e14c68bcc