k3dsdk/property_collection.cpp is missing #include <algorithm>

[lychaxo]

On my system (gcc 9.3.0 on Linux with glibc 2.30), compilation of both latest master (commit 17ef1bf) and the latest release 0.8.0.6 fails with an attempt to cast k3d::iproperty to const char * in k3dsdk/property_collection.cpp -- because GCC isn't seeing std::remove from and is instead finding the closest match of int remove(const char *) from stdio.h which is placed in the std namespace when #include'd via g++.

/tmp/SBo/k3d-k3d-0.8.0.6/k3dsdk/property_collection.cpp: In member function ‘virtual void k3d::property_collection::register_property(k3d::iproperty&)’:
/tmp/SBo/k3d-k3d-0.8.0.6/k3dsdk/property_collection.cpp:50:51: error: cannot convert ‘std::vector<k3d::iproperty*>::iterator’ {aka ‘__gnu_cxx::__normal_iterator<k3d::iproperty**, std::vector<k3d::iproperty*> >’} to ‘const char*’
   50 |  m_properties.erase(std::remove(m_properties.begin(), m_properties.end(), &Property), m_properties.end());
      |                                 ~~~~~~~~~~~~~~~~~~^~
      |                                                   |
      |                                                   std::vector<k3d::iproperty*>::iterator {aka __gnu_cxx::__normal_iterator<k3d::iproperty**, std::vector<k3d::iproperty*> >}
In file included from /usr/include/c++/9.3.0/cstdio:42,
                 from /usr/include/c++/9.3.0/ext/string_conversions.h:43,
                 from /usr/include/c++/9.3.0/bits/basic_string.h:6493,
                 from /usr/include/c++/9.3.0/string:55,
                 from /usr/include/c++/9.3.0/stdexcept:39,
                 from /usr/include/c++/9.3.0/array:39,
                 from /usr/include/c++/9.3.0/tuple:39,
                 from /usr/include/c++/9.3.0/functional:54,
                 from /usr/include/sigc++-2.0/sigc++/reference_wrapper.h:22,
                 from /usr/include/sigc++-2.0/sigc++/adaptors/bound_argument.h:24,
                 from /usr/include/sigc++-2.0/sigc++/adaptors/bind.h:6,
                 from /usr/include/sigc++-2.0/sigc++/adaptors/adaptors.h:23,
                 from /usr/include/sigc++-2.0/sigc++/sigc++.h:107,
                 from /tmp/SBo/k3d-k3d-0.8.0.6/k3dsdk/signal_system.h:23,
                 from /tmp/SBo/k3d-k3d-0.8.0.6/k3dsdk/iproperty.h:28,
                 from /tmp/SBo/k3d-k3d-0.8.0.6/k3dsdk/property_collection.cpp:24:
/usr/include/stdio.h:146:32: note:   initializing argument 1 of ‘int remove(const char*)’
  146 | extern int remove (const char *__filename) __THROW;
      |                    ~~~~~~~~~~~~^~~~~~~~~~

According to https://en.cppreference.com/w/cpp/algorithm/remove, #include needs to be added. Adding it fixes the compilation of this file.