Grantlee: Porting from Qt4-based Grantlee

Grantlee 5.3.0

Porting from Qt4-based Grantlee

Several porting steps are necessary when porting code from Grantlee 0.5 to Grantlee 5.0 and later.

# Buildsystem changes

## grantlee_add_plugin Removed

The `grantlee_add_plugin` CMake macro has been removed. Users should now use the CMake command `add_library(MODULE)`, link to the Grantlee Templates library, and use the `grantlee_adjust_plugin_name` macro with the created target.

## Grantlee_USE_FILE removed

The Grantlee_USE_FILE is obsolete and has been removed. Users should remove code such as

    include(${Grantlee_USE_FILE})

from their buildsystems.

## Use IMPORTED targets

The CMake packages shipped with Grantlee contain IMPORTED targets which should be used with the `target_link_libraries` command. Variables such as `Grantlee_TEMPLATES_LIBRARIES` are no longer provided.

Idiomatic use of Grantlee in the buildsystem is now similar to:

    find_package(Grantlee5 REQUIRED)

    add_executable(main main.cpp)
    target_link_libraries(main
      Grantlee5::Templates
    )

## CMake Package name changed

The previous major release of Grantlee shipped a CMake package findable with

    find_package(Grantlee REQUIRED)

For Grantlee 5.0 the package was renamed to include the major version number:

    find_package(Grantlee5 REQUIRED)

# C++ porting

## GRANTLEE_METATYPE_INITIALIZE macro removed

User code should simply remove the use of the macro.

## Grantlee::Node::render method is now const

The virtual method render on Grantlee::Node is now `const`. User code which creates custom plugins and overrides the render method must be updated to add the `const` too.

## LocalizedFileSystemTemplateLoader merged into FileSystemTemplateLoader

Users of `LocalizedFileSystemTemplateLoader` can now use FileSystemTemplateLoader instead.

## QSharedPointer typedefs named "Ptr" have been removed.

Replace uses of `FileSystemTemplateLoader::Ptr` with QSharedPointer<FileSystemTemplateLoader> for example.