Fix HTML errors and warnings

Issues reported by Nu Html Checker:

• Error: Stray end tag i in filter_print_view_type_toggle()
• Error: Element option without attribute label must not be empty in
  filter_draw_selection_area()
• Error: Row 7 of a row group established by a tbody element has no
  cells beginning on it
• Warning: A table row was 0 columns wide, which is less than the column
  count established by the first row (8) in filter_form_draw_inputs()
• Warning: The type attribute is unnecessary for JavaScript resources in
  html_javascript_link(), - html_javascript_cdn_link() and
  html_head_javascript()
• Error: Illegal character in query: [ is not allowed in my_view_inc.php
• Error: End tag for body seen, but there were unclosed elements in
  lost_pwd_page.php
• Error: Unclosed element div
• Warning: Consider avoiding viewport values that prevent users from
  resizing documents in layout_head_meta()
• Error: An img element must have an alt attribute, except under certain
  conditions in layout_login_page_logo()
• Error: Element div not allowed as child of element ul in this context
  in layout_breadcrumbs()

Add a new method TableGridLayout::render_spacer() to print a HTML code
for a spacer row of current table.

Add new function string_build_query() to string_api.php, a unified call
of http_build_query().

Moved the extra code from layout_page_begin() and layout_page_end() to
new paired functions layout_main_content_row_begin() and
layout_main_content_row_end().

Fixes 0035180, PR https://github.com/mantisbt/mantisbt/pull/2096