Move to Bootstrap 4

Bootstrap < 4.1.2 has the following CVE:
https://nvd.nist.gov/vuln/detail/CVE-2018-14041

Removed bootstrap-theme.css due to "Replaced the separate optional
theme with configurable options via SCSS variables
(e.g., $enable-gradients: true)."

Added "width: 100%" to a few places where width 100% was no longer
getting inherited.
Moved a few elements and adjusted styles to get the same look as
before.

See https://getbootstrap.com/docs/4.0/migration/ for more
information.

Tested: Manually on a Witherspoon.
Change-Id: I0a72665ac1ca6eacd0b553a585b1fb15e14ae62c
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/app/common/styles/layout/content.scss b/app/common/styles/layout/content.scss
index ad5e74f..5a58478 100644
--- a/app/common/styles/layout/content.scss
+++ b/app/common/styles/layout/content.scss
@@ -4,13 +4,14 @@
 
 // Page header
 .page-header {
+  width: 100%;
   position: relative;
   border-bottom: 1px solid $lightbg__grey;
   margin: .5em 0 2.2em;
   padding-left: 0;
   .h4 {
     padding: .1em 0 0 0;
-    margin: 0 0 .5em 0;
+    margin: 0 0 1em 0;
     font-weight: bold;
   }
 }
@@ -45,4 +46,4 @@
 .subhead {
   border-bottom: 1px solid $medgrey;
   padding-bottom: .5em;
-}
\ No newline at end of file
+}