Bump minimum GDAL version from 2.3 to 3.0 (#1019)

Author: gmgunter

doc/doxygen/install/centos.dox

@@ -8,7 +8,7 @@ ISCE3 has the following dependencies
 <li> Python 3.6 or above
 <li> Eigen 3.3.7 or above
 <li> Numpy
-<li> GDAL 2.3 or above with Python bindings
+<li> GDAL 3.0 or above with Python bindings
 <li> HDF5 1.10.2 or above with h5py
 <li> CMake 3.18 or above
 <li> CUDA 9.0 or above (for GPU-based processing)

doc/doxygen/install/osx.dox

@@ -7,7 +7,7 @@ ISCE has the following dependencies
 <li> C++ compiler - gcc-6/ clang-6.0 or above
 <li> Python 3.6 or above
 <li> Numpy
-<li> GDAL 2.3 or above with Python bindings
+<li> GDAL 3.0 or above with Python bindings
 <li> HDF5 1.10.2 or above with h5py
 <li> CMake 3.18 or above
 <li> ruamel yaml for python3.7

extern/CMakeLists.txt

@@ -30,7 +30,7 @@ macro(getpackage_fftw)
 endmacro()
 
 macro(getpackage_gdal)
-    find_package(GDAL 2.3 REQUIRED)
+    find_package(GDAL 3.0 REQUIRED)
 endmacro()
 
 macro(getpackage_googletest)

tools/imagesets/centos7conda/runtime/requirements.txt.main.runtime

@@ -1,5 +1,5 @@
 fftw>=3
-gdal>=2.3
+gdal>=3.0
 h5py
 hdf5>=1.10.2
 numpy

tools/imagesets/oracle8conda/runtime/requirements.txt

@@ -1,6 +1,6 @@
 backoff
 fftw>=3
-gdal>=2.3
+gdal>=3.0
 h5py
 hdf5>=1.10.2
 libgcc-ng>=9,<10