This generator collects values from the underlying generator until it
has a specified amount of them, and then returns them in one "chunk".
In case the underlying generator does not have enough elements for
a specific chunk, the left-over elements are discarded.

Closes #1538

support for generating test cases based on multiple template template
types combined with template arguments for each of the template template
types specified

e.g.
```
TEMPLATE_PRODUCT_TEST_CASE("template product","[template]",
			   (std::tuple, std::pair, std::map),
			   ((int,float),(char,double),(int,char)))
```
will effectively create 9 test cases with types:
std::tuple<int,float>
std::tuple<char,double>
std::tuple<int,char>
std::pair<int,float>
std::pair<char, double>
std::pair<int,char>
std::map<int,float>
std::map<char,double>
std::map<int,char>

Tested type is accessible in test case body as TestType
Unique name is created by appending ` - <index>` to test name
since preprocessor has some limitations in recursions

Closes #1454

Fixes #1438

This adds support for templated tests and test methods via
`TEMPLATE_TEST_CASE` and `TEMPLATE_TEST_CASE_METHOD` macros. These
work mostly just like their regular counterparts*, but take an
unlimited** number of types as their last arguments.

* Unlike the plain `TEST_CASE*` macros, the `TEMPLATE*` variants
require a tag string.

** In practice there is limit of about 300 types.

The StringMaker is off by default and can be enabled by a new macro `CATCH_CONFIG_ENABLE_VARIANT_STRINGMAKER`, to avoid increasing the footprint of stringification machinery by default.