[FEATURE] Option to hide header tags if content empty

TS option: `plugin.tx_fluidcontentcore.settings.header.hideIfEmpty`. Default behavior changed to hide headers if empty, behavior controlled through TS option or directly through template. Field can also be added as Flux form field to control this setting on a per-element basis.
[TASK] Remove schemaLocations, ship XSD

Includes XSD file at Resources/Private/Schemas/FluidcontentCore.xsd
[BUGFIX] Missing VHS namespace import in NoHeader Layout
[TASK] Implement most often used menu content types
[BUGFIX] Compatibilty for new content wizard Plugin tab
[BUGFIX] Missing removeDotsFromTS in Provider settings
[TASK] Adapt to new usage of flux:form.content
Merge pull request #61 from NamelessCoder/shipshape

[TASK] Remove schemaLocations, ship XSD
[TASK] Menu Partial: SubPagesOfSelectedPagesWithAbstract
[TASK] Remove rarely used linkToTop field
[BUGFIX] Content anchors missing hyphen glue
[TASK] Menu Partial: SubPagesOfSelectedPagesWithSections
[TASK] Menu Partial: SectionIndex
[TASK] Simplify container options and rendering
Merge pull request #63 from NamelessCoder/cleanuponaislefive

[TASK] Simplify container options and rendering
[BUGFIX] Incorrect use of "as" argument in SectionIndex Partial
[BUGFIX] Fluid syntax error
[BUGFIX] Fluid syntax error
[BUGFIX] Incorrect use of attribute/argument pragma

TagBasedViewHelper contains in initialisation method the necessary apply-attributes-to-tag methods to support all needed attributes.
[TASK] Move menu type variables to Provider

Allows the variables to be accessed from frontend rendering as well as backend editing.