This drop a lot of non-core features code and delegate their maintainance
to third parties. Also it open the door to any missing implementation
out of the box, such as Redis for the moment.
Finally this consistently enforce a constraint where there can be one and
only one active cell at any point in time in code. This used to be true for
non-default implementation of cache, but it was not true for default
implementation where all cells were kept in-memory and thus were never
detached from their worksheet and thus were all kept functionnal at any
point in time.
This inconsistency of behavior between in-memory and off-memory could
lead to bugs when changing cache system if the end-user code was badly
written. Now end-user will never be able to write buggy code in the first
place, avoiding future headache when introducing caching.
Closes#3
Over the years PclZip became a maintenance problem. It's code base
is old and the official project seems to have died out. ZipArchive
is now more commonly available and offer an easier and more complete
API. So PclZip was dropped in order to focus our efforts on what matters.
Closes#18
Third party PDF libraries must now be installed via composer and naturally
via composer autoloading mechanism. Because of that it is not necessary
to specify their path on disk. The usage is simplified and it allows us
to include them in our unit tests.
This also means that from now on PhpSpreadsheet must use composer autoloader
mechanism. The internal autoloading implementation was dropped.
We wrapped lines to make easier the source easier to read, and to have more manageable diffs.
This was done with something like:
```sh
pandoc --wrap=auto --atx-headers -f markdown -t markdown-fenced_code_attributes+pipe_tables+raw_html+intraword_underscores`
```
We aim for long pages instead of several small one, to make
`CTRL+F`ing easier and URL less prone to changes in the future.
There is still way to improve it though...
