Fixes #4543: Cache entities fetched with get_entity and elgg_get_entities
small fixes
Added entity caching to elgg_get_entities with workaround for recursive delete problem (#4568)
Merge pull request #2 from mrclay/4543_18_3

More conservative fixes to 4543-entity-caching
Fixes #4008. Sets a vertical align for admin icons consistent with the text, and set it as before (baseline) for heads.
Fixes #4643. Locks the upgrade process while it is running.
Fixes #1334. Added dropdown to change the parent of a page.
Refs #1334. Prevent cycles in the pages tree.
Refs #1334. Readded hidden input in edit page form, only on page creation.
persist 'selected' state of site menu
Refs #4643. Added unlock upgrade action.
Fixes #4725 - no longer removes file upload form outside of embed lightbox, no longer hangs on throbber when the form returns an error.
switched to matching by link name - same results, simpler code
Refs #4008. Modified CSS selector to be more specific.
Fixes #4774. Added tokens insted is_action param in delete river menu item.
Fixes #4773. Added alt attribute in page icons.
Fixes #4764: Twitter login supports persistent and referrer forwarding
Fixes #4792. Now blog author is who appears in the river.
fixes river upgrade for comments
Added jQuery-ui i18n files.